Washers with oil filter

[Q]

W126 oil filters come with 3 washers and an o-ring. The o-ring I have figured out. I assume the small copper washer is for the drain plug and the small silver washer is for the top of the oil filter housing, but where in the heck does the large copper washer go?

[pmckechnie]

Different applications, ie 450s, some diesels, etc. You can just discard them.

I'm not intimately familiar with your 450, but I don't think any of those washers are for your oil filter. I have seen 123 diesels where people have seen these washers and expect that they go on the oil filter somewhere. The only thing that is used on the oil filter is the o-ring. If there was no washer on the oil filter when you took it apart, don't feel that you have to find a place other than the trash can for the other washers.

Good luck,